How do I Make Platforms Vanish After Walking on Them

So I have been struggling with this for a while now. I want to make it so that my player Sprite can move across a solid Sprite using the platformer movement and after the player is no longer touching the platform, the platform should disappear - I can't seem to find the right event to make this happen.

Give it a variable. It's 0, in collition with player, set it to 1, you could start a timer to get rid of it.. or, when player distance is further than 30 (eg) and the variable is 1, destroy the platform.